Mycobacterial Infections In Humans Research Articles

Risk of zoonoses involving slow-growing non-tuberculous mycobacteria: Survey of antimicrobial resistance among strains from domestic and wild animals

Non-tuberculous mycobacteria are opportunistic pathogens that cause disease mainly in immunocompromised hosts. The present study assessed the prevalence of antibiotic resistance among such mycobacteria from domestic and wild animals in Croatia sampled during several years within a national surveillance program. A total of 44 isolates belonging to nine slow-growing species were genotyped and analyzed for susceptibility to 13 antimicrobials often used to treat non-tuberculous mycobacterial infections in humans. Most prevalent resistance was to moxifloxacin (77.3%), doxycycline (76.9%), and rifampicin (76.9%), followed by ciprofloxacin (65.4%), trimethoprim-sulfamethoxazole (65.4%), and linezolid (61.4%). Few isolates were resistant to rifabutin (7.7%) or amikacin (6.8%). None of the isolates was resistant to clarithromycin. Nearly all isolates (86.4%) were resistant to multiple antibiotics. Our findings suggest substantial risk that human populations may experience zoonotic infections with non-tuberculous mycobacteria that will be difficult to treat using the current generation of antibiotics. Future work should clarify how resistance emerges in wild populations of non-tuberculous mycobacteria.

Genomic features of Mycobacterium avium subsp. hominissuis isolated from pigs inJapan.

Mycobacterium avium subsp. hominissuis (MAH) is one of the most important agents causing non-tuberculosis mycobacterial infection in humans and pigs. There have been advances in genome analysis of MAH from human isolates, but studies of isolates from pigs are limited despite its potential source of infection to human. Here, we obtained 30 draft genome sequences of MAH from pigs reared in Japan. The 30 draft genomes were 4,848,678-5,620,788bp in length, comprising 4652-5388 coding genes and 46-75 (median: 47) tRNAs. All isolates had restriction modification-associated genes and 185-222 predicted virulence genes. Two isolates had tRNA arrays and one isolate had a clustered regularly interspaced short palindromic repeat (CRISPR) region. Our results will be useful for evaluation of the ecology of MAH by providing a foundation for genome-based epidemiological studies.

Tuberculins for mammals, stability of biological properties of old Koch altuber-culin (Germany) after long-term storage

The allergic method is the main one in the diagnosis of mycobacterial infections in humans and animals. Allergic diagnosis of mycobacterial infections is carried out us-ing tuberculin. Tuberculin was developed over a hundred years ago by the German microbiologist Robert Koch. The diagnostic properties of tuberculin have been studied in detail. This made it possible to develop various methods of using tuberculin in a clinical setting. In addition, tuberculin is still used in the study of the fundamental mechanisms of immunity. Until now, tuberculin is a valuable diagnostic tool. However, the stability of tu-berculin over a long period of time has not been studied. The article provides a historical overview of the manufacture and use of various types of tuberculins for mammals, as well as the results of our own research. Purpose of the study: to study the stability of the biological properties of altuberculin for mammals (Germany) after long-term storage. The study of stability was carried out according to the following parameters: activity, specificity, reactogenicity. The activity was studied in guinea pigs sensitized with M. bovis mycobacteria. The specificity was investigated in guinea pigs sensitized with M. avium mycobacteria. Reactogenicity was studied in non-sensitized guinea pigs. As a result of the research, it was found that alttuberculin for mammals is characterized by biological activity at the level of 8000 IU in accordance with the current active standard of activity (the value of biological activity should correspond to the range of 6600 IU - 15000 IU). Altuberculin is characterized by a low specificity at the level of 41% (the specificity value should not be more than 10%). Alttuberculin, in accordance with modern requirements for the quality of purified tuberculins, is characterized by a high level of reactogenicity (the value of reactogenicity is expressed in the development of inflammation, the size of which should not exceed 5 mm). Thus, Alttuberculin for mammals maintains the stability of biological properties with a shelf life of more than 70 years. A comparative analysis of the quality indicators of alttuberculin and purified tuberculin PPD indicates the preference of using the purified form of the allergen when conducting diagnostic studies of animals for tuberculosis.

Occurrence of Mycobacterium spp. in ornamental fish.

Fish mycobacteriosis is a chronic granulomatous disease caused by several species of bacteria from the genus Mycobacterium, described as nontuberculous mycobacteria (NTM). The most important species causing fish mycobacterioses are M.chelonae, M.fortuitum, and M.marinum. Mycobacteria infecting fish also include zoonotic pathogens. M.marinum is the cause of most cases of fish-related mycobacterial infection in humans. The disease occurs more frequently in workers in the fishing industry, people whose hobbies involve water activities, and aquarists. The aim of the present study was to examine the occurrence of different species of mycobacteria in freshwater ornamental fish. The occurrence of Mycobacterium spp. in freshwater ornamental fish was studied from January 2015 - December 2016. Material isolated from skin scrapings, contents of the digestive tracts, and internal organs of ornamental fish was stained with Ziehl-Neelsen (ZN) and inoculated on Lowenstein-Jensen medium. All isolates found positive by ZN were identified by amplification of the gene encoding the Hsp65 protein. A total of 408 samples obtained from 136 ornamental fish from 36 species were tested. Using the culture method Mycobacterium was isolated from 69 fish (50.1%) and 99 samples (24.3%). Sequence analysis of gene fragments coding for the Hsp65 protein of 99 isolates revealed occurrence of 13 species of mycobacteria: M. abscessus, M. chelonae, M. fortuitum, M. gordonae, M. marinum, M. mucogenicum, M. neoaurum, M. peregrinum, M. salmoniphilum, M. saopaulense, M. senegalense, M. septicum, and M. szulgai. The obtained results indicate a significant role of ornamental fish as a source of mycobacteria which are potentially dangerous,especially to humans.

Ancient but Not Forgotten: New Insights Into MPEG1, a Macrophage Perforin-Like Immune Effector.

Macrophage-expressed gene 1 [MPEG1/Perforin-2 (PRF2)] is an ancient metazoan protein belonging to the Membrane Attack Complex/Perforin (MACPF) branch of the MACPF/Cholesterol Dependent Cytolysin (CDC) superfamily of pore-forming proteins (PFPs). MACPF/CDC proteins are a large and extremely diverse superfamily that forms large transmembrane aqueous channels in target membranes. In humans, MACPFs have known roles in immunity and development. Like perforin (PRF) and the membrane attack complex (MAC), MPEG1 is also postulated to perform a role in immunity. Indeed, bioinformatic studies suggest that gene duplications of MPEG1 likely gave rise to PRF and MAC components. Studies reveal partial or complete loss of MPEG1 causes an increased susceptibility to microbial infection in both cells and animals. To this end, MPEG1 expression is upregulated in response to proinflammatory signals such as tumor necrosis factor α (TNFα) and lipopolysaccharides (LPS). Furthermore, germline mutations in MPEG1 have been identified in connection with recurrent pulmonary mycobacterial infections in humans. Structural studies on MPEG1 revealed that it can form oligomeric pre-pores and pores. Strikingly, the unusual domain arrangement within the MPEG1 architecture suggests a novel mechanism of pore formation that may have evolved to guard against unwanted lysis of the host cell. Collectively, the available data suggest that MPEG1 likely functions as an intracellular pore-forming immune effector. Herein, we review the current understanding of MPEG1 evolution, regulation, and function. Furthermore, recent structural studies of MPEG1 are discussed, including the proposed mechanisms of action for MPEG1 bactericidal activity. Lastly limitations, outstanding questions, and implications of MPEG1 models are explored in the context of the broader literature and in light of newly available structural data.

Mucosal-Associated Invariant T Cells Develop an Innate-Like Transcriptomic Program in Anti-mycobacterial Responses.

Conventional T cells exhibit a delayed response to the initial priming of peptide antigens presented by major histocompatibility complex (MHC) proteins. Unlike conventional T cells, mucosal-associated invariant T (MAIT) cells quickly respond to non-peptidic metabolite antigens presented by MHC-related protein 1 (MR1). To elucidate the MR1-dependent activation program of MAIT cells in response to mycobacterial infections, we determined the surface markers, transcriptomic profiles, and effector responses of activated human MAIT cells. Results revealed that mycobacterial-incubated antigen-presenting cells stimulated abundant human CD8+ MAIT cells to upregulate the co-expression of CD69 and CD26, as a combinatorial activation marker. Further transcriptomic analyses demonstrated that CD69+CD26++ CD8+MAIT cells highly expressed numerous genes for mediating anti-mycobacterial immune responses, including pro-inflammatory cytokines, cytolytic molecules, NK cell receptors, and transcription factors, in contrast to inactivated counterparts CD69+/−CD26+/− CD8+MAIT cells. Gene co-expression, enrichment, and pathway analyses yielded high statistical significance to strongly support that activated CD8+ MAIT cells shared gene expression and numerous pathways with NK and CD8+ T cells in activation, cytokine production, cytokine signaling, and effector functions. Flow cytometry detected that activated CD8+MAIT cells produced TNFα, IFNγ, and granulysin to inhibit mycobacterial growth and fight mycobacterial infection. Together, results strongly support that the combinatorial activation marker CD69+CD26++ labels the activated CD8+MAIT cells that develop an innate-like activation program in anti-mycobacterial immune responses. We speculate that the rapid production of anti-mycobacterial effector molecules facilitates MAIT cells to fight early mycobacterial infection in humans.

Spectroscopic Characterization of Bovine, Avian and Johnin Purified Protein Derivative (PPD) with High-Throughput Fourier Transform InfraRed-Based Method

Tuberculins purified protein derivatives (PPDs) are obtained by precipitation from heat treated mycobacteria. PPDs are used in diagnosis of mycobacterial infections in humans and animals. Bovine PPD (PPDB) is obtained from Mycobacterium bovis (Mycobacterium tuberculosis complex), while Avian PPD (PPDA) and Johnin PPD (PPDJ) are extracted, respectively, from Mycobacterium avium and M. avium subsp. paratuberculosis (M. avium complex). PPDB and PPDA are used for bovine tuberculosis diagnosis, while PPDJ is experimentally used in the immunodiagnosis of paratuberculosis. Although PPDs date back to the 19th Century, limited knowledge about their composition is currently available. The goal of our study was to evaluate Fourier Transform InfraRed (FTIR) spectroscopy as a tool to differentiate PPDB, PPDA, and three PPDJs. The results highlighted that the three PPDs have specific profiles, correlated with phylogenetic characteristics of mycobacteria used for their production. This analysis is eligible as a specific tool for different PPDs batches characterization and for the assessment of their composition. The entire PPD production may be efficiently controlled, since the N content of each preparation is related to IR spectra, with a reference spectrum for each PPD and a standardized analysis protocol.

Development of a LAMP assay for rapid and sensitive detection and differentiation of Mycobacterium avium subsp. avium and subsp. hominissuis.

Mycobacterium avium causes atypical mycobacterial infection in humans and animals worldwide. M. avium comprises the subspecies avium (MAA), hominissuis (MAH), silvaticum (MAS) and paratuberculosis (MAP). The M. avium complex (MAC), comprising M. avium and M. intracellulare, causes opportunistic infections of humans. M. avium subsp. avium (MAA) mainly causes avian tuberculosis while subsp. hominissuis (MAH) mainly infects pig. Distinguishing between these two subspecies is essential to the effective control of these atypical mycobacterial infections and minimization of the resulting economic loss. For this purpose, we developed a loop-mediated isothermal amplification (LAMP) assay that rapidly and sensitively detects and differentiates MAA and MAH. This MAA-LAMP assay targeting IS901 correctly detected four MAA isolates but did not detect 27 MAH and 19 non-MAA/non-MAH mycobacterial isolates. The MAAH-LAMP assay targeting IS1245 detected four MAA and 27 MAH isolates but not the other 19 mycobacterial isolates. We believe that implementation of this LAMP assay will significantly improve public health and safety. SIGNIFICANCE AND IMPACT OF THE STUDY: Mycobacterium avium, which is pathogenic for humans and animals, represents a continuing threat to public health and safety and to food production. Therefore, improved methods are urgently required to readily and efficiently identify M. avium subspecies. Compared with conventional PCR methods, the LAMP assay herein developed more rapidly detects and better distinguishes between two major M. avium subspecies that cause disease of pig. Importantly, this highly accurate and sensitive LAMP assay detects mycobacterial DNAs using real-time fluorescence or the unaided eye with a colour-change dye, making it ideal for translation to the clinic and slaughterhouse.

Mycobacterium scrofulaceum disease: experience from a tertiary medical centre and review of the literature

Introduction: Mycobacterium scrofulaceum infection has been identified in cases of paediatric cervical lymphadenitis but is less well defined in adults. To further characterize manifestations of M. scrofulaceum disease and treatment approaches, we reviewed our medical centre’s experience and other published reports.Methods: We performed a retrospective chart review of patients at our medical centre with a positive M. scrofulaceum culture over a 15-year period. We compare our findings with those published in the literature to identify commonalities in disease presentations and treatment outcomes.Results: We identified 17 patients in our centre with positive M. scrofulaceum cultures, 10 of whom were diagnosed with clinical infection. The types of disease encountered included pulmonary and pleural infection (4), bone and joint infections with a foreign body (2), skin and soft tissue infection (2), brain abscess (1) and paediatric cervical adenitis (1). Structural lung disease was a common finding in cases of pulmonary infection. All adult patients except those with bone and joint infections had some type of immunomodulatory condition and/or structural lung disease. In seven patients, M. scrofulaceum was isolated in urinary or respiratory cultures without signs of clinical disease.Conclusion: M. scrofulaceum is a rare cause of non-tuberculosis mycobacterial infection in humans but can infect any tissue. Adults with pulmonary disease often have underlying structural lung disease, and those with extrapulmonary disease commonly have immunosuppressive conditions or foreign body-associated infections. Treatment outcomes are generally favourable; however, in patients with pulmonary M. scrofulaceum disease prognosis is more guarded.

MicroRNAs in Mycobacterial Infection: Modulation of Host Immune Response and Apoptotic Pathways.

Our current knowledge of mycobacterial infections in humans has progressively increased over the past few decades. The infection of Mycobacterium tuberculosis causes tuberculosis (TB) disease, which has reasoned for excessive morbidity and mortality worldwide, and has become a foremost issue of health problem globally. Mycobacterium leprae, another member of the family Mycobacteriaceae, is responsible for causing a chronic disease known as leprosy that mainly affects mucosa of the upper respiratory tract, skin, peripheral nerves, and eyes. Ample amount of existing data suggests that pathogenic mycobacteria have skilled in utilizing different mechanisms to escape or offset the host immune responses. They hijack the machinery of immune cells through the modulation of microRNAs (miRs), which regulate gene expression and immune responses of the host. Evidence shows that miRs have now gained considerable attention in the research, owing to their involvement in a broad range of inflammatory processes that are further implicated in the pathogenesis of several diseases. However, the knowledge of functions of miRs during mycobacterial infections remains limited. This review summarises recent findings of differential expression of miRs, which are used to good advantage by mycobacteria in offsetting host immune responses generated against them.

Drug Susceptibility of Non-tuberculous Strains of Mycobacterium Isolated from Birds from Poland.

Mycobacterioses are a constant problem in backyard poultry, as well as pet birds. To date, no evidence of direct transmission of atypical bacilli between humans has been demonstrated, but it cannot be ruled out that sick animals can be a source of infection for people in their environment. The aim of the study was to identify mycobacteria isolated from birds with diagnosed mycobacteriosis and to determine the susceptibility of mycobacterial isolates from these animals to antituberculous drugs most commonly used in the treatment of mycobacterial infections in humans. For drug susceptibility tests, drugs such as isoniazid, rifampicin, streptomycin, ethambutol, ofloxacin, capreomycin, cycloserine and ethionamide were used. A high degree of drug resistance was demonstrated, particularly in Mycobacterium avium. Isolates of Mycobacterium xenopi showed a relatively good susceptibility to the drugs tested. The drug resistance of Mycobacterium genavense has not been determined, but this mycobacterium was identified in ten cases, which is the second most frequent occurrence in the cases studied.

Prevalence of Buruli ulcer in Osun State, Nigeria, 2016 - 2017

Introduction : buruli ulcer (BU) is a chronic debilitating, neglected but treatable tropical diseases caused by Mycobacterium ulcerans. Globally, it is the third most common mycobacterial infection in humans after tuberculosis and leprosy. There is paucity of data on the burden of BU in Nigeria. This study aimed to assess the magnitude and distribution of BU in Osun State, Nigeria.

Isolation of nontuberculous mycobacteria from soil using Middlebrook 7H10 agar with increased malachite green concentration

Environmental exposure is considered to be responsible for nontuberculous mycobacterial infections in humans. To facilitate the isolation of mycobacteria from soil, Middlebrook 7H10 agar was optimized as an enhanced selective medium by increasing the concentration of malachite green. A series of modified Middlebrook 7H10 agar media with malachite green concentrations ranging from 2.5 to 2500 mg/L was evaluated using 20 soil samples decontaminated with 3% sodium dodecyl sulfate plus 2% NaOH for 30 min. Among these modified Middlebrook 7H10 media, the medium with malachite green at a concentration of 250 mg/L, i.e., at the same concentration as in Löwenstein–Jensen medium, was the most effective in terms of the number of plates with mycobacterial growth. This medium was further evaluated with 116 soil samples. The results showed that 87.1% (101/116) of the samples produced mycobacterial growth, and 15 samples (12.9%) produced no mycobacterial growth. Of the plates inoculated with the soil samples, each in duplicate, 5.2% (12/232) showed late contamination. In total, 19 mycobacterial species were isolated, including seven (36.8%) rapidly growing mycobacteria and 12 (63.2%) slowly growing mycobacteria. Our results demonstrate that the modified Middlebrook 7H10 agar with 250 mg/L malachite green is useful for the primary isolation of nontuberculous mycobacteria from soil.

Applying the One Health Concept to Mycobacterial Research – Overcoming Parochialism

Mycobacterial infections remain a public health problem. Historically important, globally ubiquitous and with a wide host range, we are still struggling to control mycobacterial infections in humans and animals. While previous reviews have focused on individual mycobacterial infections in either humans or animals, a comprehensive review of the zoonotic aspect of mycobacteria in the context of the One Health initiative is lacking. With the purpose of providing a concise and comprehensive resource, we have collated literature to address the zoonotic potential of different mycobacterial species and elaborate on the necessity for an inter-sectorial approach to attain a new vision to combat mycobacterial infections.

Infection-Induced Vascular Permeability Aids Mycobacterial Growth.

Pathogenic mycobacteria trigger formation of organized granulomas. As granulomas mature, they induce angiogenesis and vascular permeability. Here, in a striking parallel to tumor pro-angiogenic signaling, we identify angiopoietin-2 (ANG-2) induction as an important component of vascular dysfunction during mycobacterial infection. Mycobacterial infection in humans and zebrafish results in robust induction of ANG-2 expression from macrophages and stromal cells. Using a small-molecule inhibitor closely related to one currently in clinical trials, we link ANG-2/TIE2 signaling to vascular permeability during mycobacterial infection. Targeting granuloma-induced vascular permeability via vascular endothelial-protein tyrosine phosphatase inhibition limits mycobacterial growth, suggesting a new strategy for host-directed therapies against tuberculosis.

S100A12 Is Part of the Antimicrobial Network against Mycobacterium leprae in Human Macrophages.

Triggering antimicrobial mechanisms in macrophages infected with intracellular pathogens, such as mycobacteria, is critical to host defense against the infection. To uncover the unique and shared antimicrobial networks induced by the innate and adaptive immune systems, gene expression profiles generated by RNA sequencing (RNAseq) from human monocyte-derived macrophages (MDMs) activated with TLR2/1 ligand (TLR2/1L) or IFN-γ were analyzed. Weighed gene correlation network analysis identified modules of genes strongly correlated with TLR2/1L or IFN-γ that were linked by the “defense response” gene ontology term. The common TLR2/1L and IFN-γ inducible human macrophage host defense network contained 16 antimicrobial response genes, including S100A12, which was one of the most highly induced genes by TLR2/1L. There is limited information on the role of S100A12 in infectious disease, leading us to test the hypothesis that S100A12 contributes to host defense against mycobacterial infection in humans. We show that S100A12 is sufficient to directly kill Mycobacterium tuberculosis and Mycobacterium leprae. We also demonstrate that S100A12 is required for TLR2/1L and IFN-γ induced antimicrobial activity against M. leprae in infected macrophages. At the site of disease in leprosy, we found that S100A12 was more strongly expressed in skin lesions from tuberculoid leprosy (T-lep), the self-limiting form of the disease, compared to lepromatous leprosy (L-lep), the progressive form of the disease. These data suggest that S100A12 is part of an innate and adaptive inducible antimicrobial network that contributes to host defense against mycobacteria in infected macrophages.

Association of Human Antibodies to Arabinomannan With Enhanced Mycobacterial Opsonophagocytosis and Intracellular Growth Reduction.

Background. The relevance of antibodies (Abs) in the defense against Mycobacterium tuberculosis infection remains uncertain. We investigated the role of Abs to the mycobacterial capsular polysaccharide arabinomannan (AM) and its oligosaccharide (OS) fragments in humans.Methods. Sera obtained from 29 healthy adults before and after primary or secondary bacillus Calmette-Guerin (BCG) vaccination were assessed for Ab responses to AM via enzyme-linked immunosorbent assays, and to AM OS epitopes via novel glycan microarrays. Effects of prevaccination and postvaccination sera on BCG phagocytosis and intracellular survival were assessed in human macrophages.Results. Immunoglobulin G (IgG) responses to AM increased significantly 4–8 weeks after vaccination (P < .01), and sera were able to opsonize BCG and M. tuberculosis grown in both the absence and the presence of detergent. Phagocytosis and intracellular growth inhibition were significantly enhanced when BCG was opsonized with postvaccination sera (P < .01), and these enhancements correlated significantly with IgG titers to AM (P < .05), particularly with reactivity to 3 AM OS epitopes (P < .05). Furthermore, increased phagolysosomal fusion was observed with postvaccination sera.Conclusions. Our results provide further evidence for a role of Ab-mediated immunity to tuberculosis and suggest that IgG to AM, especially to some of its OS epitopes, could contribute to the defense against mycobacterial infection in humans.

Methods used in preclinical assessment of anti-Buruli ulcer agents: A global perspective.

Buruli ulcer (BU) caused by Mycobacterium ulcerans is the third most common chronic mycobacterial infection in humans. Approximately 5000 cases are reported annually from at least 33 countries around the globe, especially in rural African communities. Even though anti-mycobacterial therapy is often effective for early nodular or ulcerative lesions, surgery is sometimes employed for aiding wound healing and correction of deformities. The usefulness of the antibiotherapy nonetheless is challenged by huge restrictive factors such as high cost, surgical scars and loss of income due to loss of man-hours, and in some instances employment. For these reasons, more effective and safer drugs are urgently needed, and research programs into alternative therapeutics including investigation of natural products should be encouraged. There is the need for appropriate susceptibility testing methods for the evaluation of potency. A number of biological assay methodologies are in current use, ranging from the classical agar and broth dilution assay formats, to radiorespirometric, dye-based, and fluorescent/luminescence reporter assays. Mice, rats, armadillo, guinea pigs, monkeys, grass cutters and lizards have been suggested as animal models for Buruli ulcer. This review presents an overview of in vitro and in vivo susceptibility testing methods developed so far for the determination of anti-Buruli ulcer activity of natural products and derivatives.

Mycobacterium tuberculosis EspB protein suppresses interferon-γ-induced autophagy in murine macrophages.

Mycobacterium tuberculosis (Mtb) persists within immature phagosomes by preventing their maturation into phagolysosomes. Although the early secretory antigenic target 6 (ESAT-6) system 1 (ESX-1) secretion-associated protein B (EspB) of Mtb is strongly linked to immunogenicity and virulence of this organism, its mechanism of action remains largely unclear. This study aimed to investigate EspB effects on autophagy in murine ANA-1 macrophage cells. EspB gene was amplified by polymerase chain reaction from Mtb H37Rv genomic DNA to express recombinant EspB protein. Levels of autophagic markers, including Microtubule-associated protein 1 light chain 3 beta (LC3B-I and -II), phosphorylated signal transducer and activator of transcription (STAT)1 and total STAT1 in ANA-1 cells treated with EspB proteins were assessed by Western blotting. In addition, autophagic vacuoles were detected by fluorescence microscopy. Finally, IFN-γR1 expression was evaluated by semiquantitative reverse transcriptase polymerase chain reaction and flow cytometry. EspB gene was expressed in Escherichia coli cells to yield a soluble N-terminal glutatione S-transferase tag fusion protein used in subsequent experiments. Preincubation with EspB significantly suppressed autophagosome formation and LC3B expression induced by interferon (IFN)-γ stimulation, in a dose-dependent manner. These results were confirmed by the reduced incorporation of monodansylcadaverine, a marker for the acidic compartment of autolysosomes, after treatment with EspB. Interestingly, we found that IFN-γ receptor 1 mRNA and protein levels were decreased in EspB-stimulated ANA-1 cells in comparison with untreated cells. Finally, EspB protein also inhibited IFN-γ-activated STAT1 phosphorylation, thereby downmodulating macrophage responsiveness to IFN-γ. EspB inhibits autophagosome formation in murine macrophages, at least in part by downregulating IFN-γ receptor 1 expression. Overall, EspB should be considered a relevant factor in the pathogenesis of mycobacterial infections in humans.

Occurrence of nontuberculous mycobacteria in aquatic sources of Sri Lanka

Nontuberculous mycobacteria (NTM) have been reported to cause opportunistic infections with increasing frequency, especially in immunocompromised patients. Water plays a major role in the epidemiology of nontuberculous mycobacterial infection in humans, as it is one of the natural sources for transmission of this group of organisms. The current study focused on determining the occurrence of NTM in different aquatic sources of Sri Lanka by using phenotypic tests and polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis of the rpoβ gene. Of 290 water samples, 45 (15%) were positive for NTM on culture. The percentage of mycobacteria identified at species level by phenotypic tests and PCR–RFLP analysis were 44% (20/45) and 73% (33/45), respectively. The frequency of isolation of mycobacteria from aquarium water, surface water, ground water and chlorinated water were 29% (20/70), 26% (20/76), 5% (4/76) and 1% (1/68), respectively. Eleven different NTM species were identified by PCR–RFLP analysis. M. fortuitum type I was the most frequently isolated species from all the four water sources. The current study suggests that water is an environmental source harboring NTM, a potential public health hazard especially for those with immunodeficiency.